Flexible cable conduit joints

ABSTRACT

A joint coupling is provided for a flexible cable conduit, which conduit has an inner case and an outer coaxial sheath. The coupling comprises a two-part collet the two parts of which are of different diameters and are disposed in axially consecutive relationship, the part of smaller diameter being lodged in an externally threaded union while the larger diameter part is lodged in a nut received by the union. The collet parts and the union and nut have cooperating conical faces so that as the nut is screwed on to the union both collet parts are contracted.

United States Patent inventor James Frederick Hemens Redhill, Surrey,England Appl. No. 794,568 Filed Jan. 28, 1969 Patented Apr. 27, 1971Assignee Arens Controls Limited Redhill, Surrey, England Priority Mar.5, 1968 Great Britain 10,684/68 FLEXIBLE CABLE CONDUIT `lOlNTS 3 claims,1 Drawing Fig.

U.s.c|.. 28s/149, Y 174/8s,285/322,2s5/341 intel F161 39/00 Field ofswdi285/133, 382.7, 149, 341, 322,323, 13s; 334/89, 27o;

1 J'IIIIIM 'IIIA Primary Examiner-Dave W. Arola Attorney-Dowell andDowell ABSTRACT: A joint coupling is provided for a flexible cableconduit, which conduit has an inner case and an outer coaxial sheath.The coupling comprises a two-part collet the two parts of which are ofdifferent diameters and are disposed in axially consecutiverelationship, the part of smaller diameter being lodged in an externallythreaded union while the larger diameter part is lodged in a nutreceived by the union. The collet parts and the union and nut havecooperating conical faces so that as the nut is screwed on to the unionboth collet parts are contracted.

. let assembly This invention relates to the jointing of conduit, moreparticularly conduit having a composite construction where one conduitcase is disposed concentrically within another case. The two conduitcases are normally employed to fulfill different functional requirementsof the integrated assembly.

One use of this type of conduit is in mechanical remote controltransmission cables wherein the mechanical effort is transmitted by aninner cable wire guided by the surrounding conduit. Such conduit maycomprise a liner tube encircled by a helix of high tensile wires woundin a relatively long lay about the liner tube. These high tensile wiresare retained in place by a plastic casing which is extruded in the formof a concentric l sheath.

One object of the invention is to provide a double collet as sembly, thecollets being disposed end to end with their larger ends contiguous, onecollet gripping the lay wires and being contracted by forcing into aconical mouth of a union member, while the other collet of largerdiameter grips the -direction contracting the collet. This means thatthe larger diameter collet gripping the plastic sheathing tracted to acertain is only conpredetermined limited extent, whereafter furtherscrewing of the nut on to the union member further contracts the smalldiameter collet gripping the conduit lay wires, by reason of the end toend engagement of the two collets, but does not any further contract thelarger diameter collet gripping the plastic sheathing. This enables anydesired gripping force to be applied between the smaller diameter colletand the lay wires without the gripping force between the larger diametercollet and the plastic sheathing being increased to the point where thesofter sheathing will be injured.

An object of the present invention is to provide a secure coupling meanswhich is capable of being assembled in the field without special tools.

According to the invention, a conduit coupling comprises a radiallycontracting collet assembly having a stepped internal diameter such thattwo concentric conduits are simultaneously gripped by the two portionsof of different diameters. Such a collet can be made up of two case ofthe cable conduit described, nal diameter grips the long lay wires whilethe part of larger internal diameter grips the outer plastic sheathing.

Preferably, the larger part of the collet is provided willi an externalabutment to limit the extent of its radial contraction. Either thelarger or the smaller part, or both, may be formed internally with anaxially discontinuous surface, for example like a truncated threadform', to improve its grip.

One form of construction in accordance with the invention is illustratedby way of example in the accompanying drawing, which shows, in partiallongitudinal section, a cable conduit joint.

ln the drawing, a conduit ll for a mechanical transmission cable isreceived in one end of a double-ended coupling assembly l2. The cableconduit comprises an inner liner tube 13, a long lay of helical wires 14and an outer plastic sheathing l5. The coupling assembly comprises anexternally threaded union member I6 on which is received a nut 17; adouble col- 18 to grip the conduit ll is housed within the end oftheunion 16 and the nut l7.

The collet assembly comprises two axially consecutive parts 19, ofdifferent nominal diameters arranged back to back in contiguity. Thelarger diameter part 19 lies beyond the union 16 and within the nut 17,while the smaller diameter pnrt 20 is within the end ol the unionmember. The two parta of the collet have external conical surfaces 2l,22 of opposite slope and these cooperate, respectively, with internalconed surfaces 23, 24 in the nut and the union whereby when the nut isscrewed farther on to the union end both portions of the collet arecontracted simultaneously.

The inner tube 13 and surrounding wires and 26, the thread form in thesmaller diameter part 20 being deeper than that in the larger diameterpart 19.

The nut 17 has an internal shoulder 27 which engages an externalabutment surface 28 on the collet part 19 for positively limiting radialcontraction of this part of the collet.

lclaim:

l. A conduit joint assembly for a flexible mechanical transmissioncable, comprising in combination: a flexible conduit having an innerliner tube, a lay of helical wires around said liner tube, and an outerplastic sheathing covering said lay of helical wires, said conduitfurther having a bared end portion by said liner tube and said lay ofhelical wires protruding together beyond the end of said plasticsheathing, an externally screw-threaded union member having anaxially-extending bore receiving within it said bared end portion ofsaid conduit which union member bore is formed with an entry mouth whichdiverges conically up to the end of said bore at which said bared endportion of said conduit enters it, a nut which is internallyscrew-threaded for only a part of its length extending up to one endthereof said nut being disposed with the nonscrew-threaded part of itslength surrounding an end portion of said plastic sheathing of' saidconduit and with the screwthreaded part of its length extending intooverlapping screwed engagement with said externally screw-threaded unionmember, said nonscrew-threaded portion of said nut length surroundingsaid plastic sheathing being formed internally with a conicallyincreasing bore section that diverges in the opposite axial direction tothe divergent mouth of said union member bore, said conically increasingbore section of said nut terminating at its larger diameter end nearersaid union member in a more abrupt increase in the internal diameter ofsaid nut thereby forming an internal shoulder within said nut, firstcontractable collet means disposed in said union member divergent moutharound said bared end portion of said conduit and having a nominallycylindrical internal surface in engagement with said lay of helicalwires of said conduit, said first collet means further having aconically enlarging outer surface contiguous with said conicallydivergent mouth of said union member bore, and second contractablecollet means of larger internal diameter and larger maximum externaldiameter than said first collet means and disposed within said nut incontiguous end-to-end relationship with said first collet means, saidsecond collet means having a nominally cylindrical internal surface inengagement with said plastic sheathing of said conduit, said secondcollet means further having a conically enlarging outer surfacecontiguous with said conically increasing bore section of said nut andterminating at its end of larger diameter in a more abrupt increase inthe external diameter of said second collet means thereby forming anexternal shoulder on said second collet means lying between saidinternal shoulder on said nut and said first collet means andconstituting in cooperation with said internal shoulder on said nut astop abutment to limit relative axial movement of said nut and secondcollet means in the direction bringing about contraction of said secondcollet means.

2. A joint assembly according to claim l, wherein said first colletmeans is formed internally with an axially discontinuous surface toimprove its grip.

3. A joint assembly according to claim l, wherein said second colletmeans is formed internally with an axially discontinuous surface toimprove its grip.

1. A conduit joint assembly for a flexible mechanical transmissioncable, comprising in combination: a flexible conduit having an innerliner tube, a lay of helical wires around said liner tube, and an outerplastic sheathing covering said lay of helical wires, said conduitfurther having a bared end portion formed by said liner tube and saidlay of helical wires protruding together beyond the end of said plasticsheathing, an externally screw-threaded union member having anaxiallyextending bore receiving within it said bared end portion of saidconduit which union member bore is formed with an entry mouth whichdiverges conically up to the end of said bore at which said bared endportion of said conduit enters it, a nut which is internallyscrew-threaded for only a part of its length extending up to one endthereof said nut being disposed with the nonscrewthreaded part of itslength surrounding an end portion of said plastic sheathing of saidconduit and with the screw-threaded part of its length extending intooverlapping screwed engagement with said externally screw-threaded unionmember, said nonscrewthreaded portion of said nut length surroundingsaid plastic sheathing being formed internally with a conicallyincreasing bore section that diverges in the opposite axial direction tothe divergent mouth of said union member bore, said conically increasingbore section of said nut terminating at its larger diameter end nearersaid union member in a more abrupt increase in the internal diameter ofSaid nut thereby forming an internal shoulder within said nut, firstcontractable collet means disposed in said union member divergent moutharound said bared end portion of said conduit and having a nominallycylindrical internal surface in engagement with said lay of helicalwires of said conduit, said first collet means further having aconically enlarging outer surface contiguous with said conicallydivergent mouth of said union member bore, and second contractablecollet means of larger internal diameter and larger maximum externaldiameter than said first collet means and disposed within said nut incontiguous end-to-end relationship with said first collet means, saidsecond collet means having a nominally cylindrical internal surface inengagement with said plastic sheathing of said conduit, said secondcollet means further having a conically enlarging outer surfacecontiguous with said conically increasing bore section of said nut andterminating at its end of larger diameter in a more abrupt increase inthe external diameter of said second collet means thereby forming anexternal shoulder on said second collet means lying between saidinternal shoulder on said nut and said first collet means andconstituting in cooperation with said internal shoulder on said nut astop abutment to limit relative axial movement of said nut and secondcollet means in the direction bringing about contraction of said secondcollet means.
 2. A joint assembly according to claim 1, wherein saidfirst collet means is formed internally with an axially discontinuoussurface to improve its grip.
 3. A joint assembly according to claim 1,wherein said second collet means is formed internally with an axiallydiscontinuous surface to improve its grip.